Circuit interrupter



May 20, 1941.

L. R LUDWIG CIRCUIT INTERRUPTER `Filed July'l, 1938 4 Sheets-Sheet 1 www4 Sheets-Sheet 2 mf/a @my Filed July 1, 193B L. R LUDWIG IRcUITNTERRUPTER Mgy zo, 1941.

May 20, 1941. L R, Upwlg 2,243,038

CIRCUIT INTERRUPTER.

Filed July 1, 1938 4 Sheets-Sheet 3 WITNESSE'S: INVENTOR ATTORNEYPatented May 20, 1941 UNITED sTATEs PATENT oFFicE Leon B. to lWestinghouse Electric a Manufacturing Company, East Pittsburgh,

' Pennsylvania Pa., a corporation of Application July 1, 1938, SerialNo. 216,884

19Ciainis.

This invention relates to circuit interrupters,

and more particularly to arc extinguishers for circuit interrupters ofthe air break type. It is an object oi my invention to provide an airbreak circuit interruptcr which not only interrupts the circuit, butalso restricts and deionines the arc gases so as to prevent the issuanceof dame from the interrupting structure, thereby rendering theinterrupter suitable for close mounting in metal cubicles or other'enclosed structure.

A further object of my invention is to increase the interruptingcapacity f circuit interi-unters of the aforesaid type.

Another object of my invention remdes in the provision of anarc-extinguishing device for air.

circuit breakers of high interrupting capacity, which device is equallyeffective on alternating and direct-current circuits. A

A more specific object ot my invention is the provision of anarc-extinguishing device -for an air circuit breaker of the aforesaidtype in which improved arc extinction is obtained by the use of spacedslotted plates of insulating material.

and in which. arc movement within the slots is obtained by aself-contained magnetic iield device thereby eliminating the necessityof a blowout coil or coils to secure arc movement.

Other objects and advautagesrelate to detalls of the interruptingstructure such as the thickness of the interrupting plates, the spacingtherebetweim, the shape of the arc receiving slots and the like. all ofwhich will appear more fully in the following description when taken inconnection with .the accompanying drawings, in which:

Figure 1 shows the circuit interrupter of my invention in sideelevation, a portion oi .the arcextinguishing structure being brokenaway to reveal tlie position of the arc drawing contacts with respect tothe arc-extinguishing device;

Fig. 2 is an enlarged side elevation view partially in section of thearc-extinguishing device group of plates forming Dart of thearc-extlnguishing device shown in the previous figures;Fig.6isanendelevationviewotamodiiled form of plate structure which maybe used in the -arc-extinguishing device of my invention;

Fig. 'I is a fragmentary sectional view of the plate structure shown AinFig. 6. 4taken' along .the line VII-V11 thereof: g

Fig. 8 is a fragmentary sectional view showing a plate structure for anarc-extinguishing device similar to that shown in Fig. '7 except thatthe plates of magnetic material have been omitted;

Fig. 9 is a plan view showing a further form of plate structure capableoi use in the arc-extinguisher of my invention;

Fig. 10 is a sectional view o1' the plate structure shown in Fig. 9taken along the line X-X thereof Fig. 1l is a sectional View of theplate structure shown in Fig. 10, taken along the line XI-XI thereofFig. l2 is an elevation view showing still another arrangement of platestructure capable of use in the arc-extinguisher of my invention; and

Fig. 13 is a sectional view of the plate structure shown in Fig. 12,taken along the line XIII-m1 thereof.

In order to accomplish arc extinction without the issuance of ameexteriorly oi the arc-extinguishng structure,l numerous devices haveheretofore been proposed. One form of ard-extinguishing structure whichhas proven to be successful commercially comprises a lplurality ofspaced metallic plates having, aligned arc receiving slots therein. Thearc to be extinguished is drawn within or at the entrance portion of theslots and is moved to the closed end of the slots, and nally into themetallic plates where it is caused to play as a series of short arcsbetween the plates. The metal plates in this instance quickly deionize'the arc stream and bring about arc extinction without the issuance ofame from the vent passages between the plates. Although this type ofcircuit interrupter has proven to be effective in interrupting circuitscarrying as high as 32,000 amperes at 15,000 volts, great diiilculty isencountered in causing currents of substantia-ily greater magnitude toproperly transfer to the metallic delonizing plates.

I have discovered that an arc-extinguishing structure employing aplurality of spaced plates of insulating non-gas forming material havingaligned arc-receiving slots therein is far more eilective than the knownarc-extinguishing structure employing metallic plates, and is capable o!materially extending the upper limit of current capable of beinginterrupted. One embodiment of the interrupter which will be hereinafterdescribed in detail, is capable oi producing complete circuitinterruption oi v125.000 amper-es at 600 volts alternating current withonly 1/2 cycle of arcing. When connected to a direct-current circuit theinterrupter is capable of interrupting up to 80,000 ampere's or more at750 volts.

The improved interrupting power of my arcextinguishing structure isbased upon the magnetic blast theory and is explained as follows. If anarc is moved laterally in air by a suitable magnetic ileld against anon-gas-producing solid of such shape that no turbulent flow of gas isproduced, the section of the are remains substantially unchanged andonly a slight increase in pressure of the arc gas results. The arcvoltage is increased somewhat due to the loss of ions and heat to therestricting walls of the solid. Now if slots or vent openings are placedalong the restricting wall sothat the pressure is relieved, a strongblast of gas passes through the openings. The arc must, therefore,ionize fresh gas in considerable quantties'in order to maintain itselfand the arc voltage is thereby greatly increased.

In other words, the eil'ect of the magnetic field is to move ions out ofthe arc stream. The force exerted by the magnetic fleld on the ions istransmitted to the gas surrounding the arc in collisions between theions and the neutral gas mole.- cules. Thus, the moving ions causeun-ionized gas to be placed in motion so that a new supply of coolu1u-ionized gas is constantly being drawn past the arc. Of course, theions which are moved into the venting slots will cause the arc to loopor bow somewhat into the slots since the arc attempts to follow themovement of the ions. However, the increasing flow of un-ionized gasinto the arc increases the rate of deionization so that in case ofalternating current, the arc path quickly becomes non-conductingfollowing a current zero.A 'I'he rapidly escaping ions through theventing slots as well as the blast of unionized gas caused by themagnetic eld, produces a rapid rise in arc voltage so as to make themethod of arc extinction equally effective on direct current. Arcextinction with the circuit interrupter of my invention is, therefore,accomplished in a manner different from that employed in liquid immersedbreakers which subject the arc to a combined blast of arc extinguishingliquid and the products of decomposition of the arc. There is also amarked difference in the manner of arc extinction with my structure andthat employed in air or gas blast breakers as heretofore used. Gas blastand air breakers of the prior art depend upon rapid lengthening of thearc by either magnetic or gas blast blowout means for extinguishing thearc. In my invention, there is substantially no lengthening of the arcas initially drawnnor is the arc split into a plurality of shortserially related sections, as in metallic plate deionizing structures.The specific structure of one device with which I have accomplished myimproved results will now be' described.

In Fig. 1 of the drawings, the reference numeral l5 designates a panelupon which the interrupter of my invention is mounted. 'I'he panel Ilsupports a frame i1 which carries a suitable operating mechanismgenerally indicated at I9.

.The operating mechanism I! is not specifically claimed herein and maybe of any suitable arrangement, as for instance, that shown in PatentNo. 2,177,014, issued October 24, 1939, to W. M. Austin, and assigned tothe assignee of the instant application.

,The operating mechanism Il is adaptedI to actuate a pivoted contactcarrying arm 2| hinged to a cross pin 23 to the frame I1. The contactarm 2| supports a main bridging contact 2l, the ends of which areadapted to normally engage the main line contacts 21 and 29. Connectedto the main contact 21 is an arcing contact Il adapted to cooperate witha moving arcing contact Il carried by a suitable arm. 25 supported bythe pivoted arm 2l. Inasmuch as the specific contact arrangement is notspecifically claimed in the instant application, further details of Athecontact structure may be had 4by referring to Patent No. 2,214,471,issued September 10, 1940,

to L. R. Ludwig and M. E. Horne, and also assigned to the assignee ofthe instant application.

An arc established by the separation of the arcing contacts 3| and 33 isextinguished by an arc-extinguishing device 31 disposed in partiallysurrounding relation with respect to the arcing contacts. Thearc-extinguishing device 31 is more specifically illustrated in Figs. 2to 5 inclusive, and comprises a back support plate Il of insulatingmaterial and a front support plate 4l also of insulating material,between which are disposed a plurality of plates of insulating materialspaced from each other by plates of magneticmaterial. The general shapeand arrangement of these plates are more clearly shown in Fig. 5, whichrepresents a group of plates disposed within the space indicated by thebracket at X in Fig. 2.

As shown in Fig. 5, the lowermost plate 43 is constructed of insulatingmaterial and preferably of refractory or other material that issubstantially free from substance which gives off gas when acted upon byan arc such for example as asbestos board, quartz, soap stone ortitanium oxide. Cold molded compositions as vfor instance a productknown as artificial porcelain comprising 30% talc, 2% feldspar and 68%clay may also be used. In general all materials which are refractory innature and have the requisite mechanical strength are suitable for thispurpose. The preference for non-gas forming materials will be made knownhereinafter. The plate 43 is provided with a notch or slot 45 extendingfrom the lower end thereof inwardly and tapers from a relatively wideWidth at the edge of the plate to a narrow slot-like portion at theclosed end thereof. The outline of the slot 45 is perhaps more clearlyshown in Fig. 3. Adjacent the plate 43 disposed on either side of theslot 45, is a pair of plates 41 of magnetic material, such as iron orsteel, which serve as spacers between the insulating plate 43 and thenext adjacent insulating plate 49. The iron plates 41 also serve toproduce a magnetic field to facilitate arc movement upwardly in the slot45, as will be explained more fully hereinafter.

The plate 49 is similar in construction to plate 43, with the exceptionthat it is somewhat shorter and is adapted to support a transverselyextending plate 5| of magnetic material across the upper end thereof,the purpose of which will also appear hereinafter. Two sets of plates 41are also disposed between the plate 49 and a plate 5l, the latter platebeing similar to plate 4I, with the exception that the entrance portionof its slot 45 has been extended and is of a smooth contour,

whereas the entrance portion of the slot 45 in plate 43 `is providedwith two arcuate cutout portions, as shown at 55, for the purpose ofaccommodating the fixed arcing contact structure 3l.

With particular reference to Fig. 2 the insulating plates to the rightof the portion indicated at X have identically the same slot contourasthat shown by the plate 53 in Fig. 5. The insulating plates to the leftof the portion indicated at X have the same slot contour as plate 43.

Each of the plates 43, 43 and 53 of insulating material, as well as theplates 41 of magnetic material, are provided with apertures l1 as shownin Figures 3 and 5. These apertures permit the assembly ofthe respectiveplates in the order shown upon four tubular members. 53 of insulatingmaterial. 'I'he stack of plates is firmly held together by bolts 5ipassing through the two lowermost tubular members 53 and the respectivefront and back supports 33 and 4i. Either side of the plate assembly lsprovided with a cover plate 53 secured to the respective front and backsupports by screws 35, as shown. The plates 5i of magnetic materialdisposed in abutting relation with respect to the plates 43, areprevented from movement away from the plates 43 by means of bar members51 secured to each of the side plates well as the cross-sectional areaof the venting passage between the plates. In practice. I have foundthat the plates of insulating material may 33, and which register withthe rectangular detents 53 provided in the plates 5i.

The front support 4i is also provided with al lwhich are anchored tosuitablefastening means not shown, provided in the panel. Thearc-extinguishing device 31 is positioned with respect to the fixedarcing contact 3| by means of a semicircular support 15 which forms partof the fixed arcing contact assembly and upon which `the back supportplate 33 is adapted to rest. In order to properly center thearc-extinguishing device 31, the back support plate 33 is provided witha semi-circular notch or detent 11 as more clearly shown in Figs. 2 and3. The support member 15 is adapted to register with the notch 11 whenthe arc-extinguishing structure 31 is in place. When Athus positionedand with movement of the arcing contact 33 to the open position, thepath of movement of the contact 33 takes place centrally within thealigned slots 45 of the respective plates of insulating material.

When an arc is established by the separation of contacts 3| and 33, theplates 41 of magnetic material cause the arc to be moved upwardly in theslots 45 towards the closed end thereof. The magnetic reaction isincreased by the transversely extending plates 5I disposed in abuttingrelation with the plates of insulating material 43. It will also beobserved that the transverse plates 5I of magnetic material are of thesame thickness as the plates 43 of insulating material, so that theplates 41 of magnetic material provide a venting space or channelbetween adjacent plates of insulating material that is free andunobstructed. Thus as the arc is drawn between the. arcing contacts 3iand 33, and moves to the closed end of the slots 45 in accordance withthe foregoing theory, it will be subjected to a strong blast of gas setup by the magnetic eld moving the arc upwardly. The use of gas-forminginsulating material for the plates 43, 43 and 53 is undesirable in thatthe action of the arc upon such material produces gas in such quantitiesso as to act expulsively upon the arc which tends to blow the arc out ofthe slots 45 and in general hinders arc movement towards the closed endsof the slots. The arc is prevented from being moved or looped asubstantial distance between the plates of in.

sulating material by the proper selection of thickness of the insulatingplates. and also the spacing between the plates of insulating material,as

vary from $6" to V4 and the spacing between plates of insulatingmaterial may vary from Y." to M4". The plates of magnetic material 41preferably have such a width that 'the space therebetween at the mostconstricted portion is from y. square inch to 3/4 square inch. I havefound that if the cross-sectional area of the venting passages is toogreat, there is a marked tendency for the arc to elongate and be driventhrough the venting passages and out the open end thereof.

I have also discovered that the shape of the slot 45 is of importance inobtaining free and unimpeded movement of the arc, particularly of thehigher current values upwardly towards the closed ends of the slots. Forexample, I have found that a slot that varies in width from at its apexto 1/3" .at a point two inches removed therefrom, has Substantially theproper taper at its upper or extremely narrow end. The lower portion ofthe slot, however, may increase in width more rapidly and so long as thesides thereof have a smooth contour and are of sumcient width to permitthe moving arcing contact 33 to pass therethrough, no diiliculty isexperienced in obtaining the requisite arc movement. In general, theshape of the slot 45 may be such that increases as l increases, where lis the distance measured along the axis of the slot from its apex and wis the width of the slot measured perpendicular to the axis. The taperor the rate at which the slot changes its width may also be expressed ashalving in width in every longitudinal distance of from to 2 inches.

In order to prevent gases resulting from an arc within the slots 45 atthe time of contact separation or shortly thereafter from being directeddownwardly and against the circuit interrupter contact mechanism, I haveprovided two opposed deflecting members 13 disposed on either side ofthe path of movement of the contact 33, and respectively secured to theside cover members 83. The deflecting members 13 provide a throat ororifice-like passage in which moving contact 33 operates, and furtherprovides a pocket immediately above the members, in which the gases areentrapped, deflected and caused to be directed upwardly in the eventthat the current being interrupted is suiliciently great to cause ablast of gas having a tendency for downward movement. This tendency fordownward movement, however, persists only for a short interval of timeand gives way to the effect of the magnetic field which drives the arcgases as well as considerable quantities of un-ionized gas upwardly ofthe slots and through the spaces between the plates of insulatingmaterial.

I have also discovered that effective arc extinction may be attained by.modifying the plate arrangement within the arc-extinguisher 31 as shownin Figs. 6 and '7. As shown `in these two figures, a plate 3l ofinsulating material, having a slot 33 therein, is placed on either sideof a plate 35 of magnetic material having a slot 31 in Fig. '7 andassembled with spacing members 88 disposed therebetween so as to providevent passages adjacent the arc and through which a blast of gas may bedirected to aid in extinguishing the arc.

Although the plates of magnetic material prcduce superior performance, Ihave also discovered that a successful arc-extinguishing struc-n turemay be produced by the use of spaced plates of insulating materialwithout plates of magnetic material or other magnetic means disposedthere between, as shown in Fig. 8. In Fig. il the platesJ 8| correspondin shape to the plates 8| oi Fig. d, and are provided with spacers B9without the use of magnetic material. The absence of iron or othersuitable magnetic material in the arcextinguishing device asschematically illustrated in Fig, 8, permits a more rapid rise of arcvolt age but also has the tendency of permitting the arc to be blownthrough the venting spaces between the plates of insulating material andappear exteriorly of the arc-extinguishing device before the arc isextinguished.l The addition of iron or other magnetic material to thearc-` extinguishing structure has a marked inductive effect and greatlyreduces the transient voltage rise preceding current interruption, and.also limits the amount of movement of the arc into the venting spacesbetween the plates of insulating material, thereby lessening the dangerof flame from appearing exteriorly of the arcextinguishing device.Therefore, a further advantage in the use of magnetic material in thearc-extinguishing structure resides in the provision of means formovingthe arc quickly towards the apex of the slots in the plates ofinsulating material without movement of the arc beyond the ends of theplates.

In-Figs. 9 to 11, a modified plate structure is illustrated in whichplates of insulating material ill are spaced from each other by narrowplates 93 of magnetic material disposed on either side of thearc-receiving slot 95. The magnetic eiect of the plates 93 of magneticmaterial is strengthened by the addition of a yoke 91, also of magneticmaterial, disposed about the upper end of the plate assembly. Thearc-extinguishing operation, however, is performed in a manner asheretofore described. I

Figs. 12 and 13 illustrate a further possibility of plate structurewhich constitutes alternate plates of insulating material having a. slot|03 therein and plates |05 of magnetic material of inverted U-shape, asshown in Fig. 12. Thus the plates provide a spacing between the platesof insulating material and also -provide a strong magnetic field formoving the arc towards the closed end of the slot III. The plates |05 inthis instance are of considerably greater length than the plates IDI soas to pro vide a suitable venting passage |01 between the adjacentplates of insulating material.

Although I have shown and described a specificil circuit interruptor anda number ofarc-cxtin guishing devices therefor, it is to be understoodthat the same is for the purpose of illustration and that changes andmodifications may be made by those skilled in the art without* departingfrom the spirit and scope of the appended claims.

I claim as myinvention:

1. In a .circuit interrupter, means for establishing an arc, anarc-extinguishing structure for extinguishing said arc comprising meansof insulating material having a. V-shaped slot therein decreasingprogressively 'in width from t `ne side lil in which said are is adaptedto play, said slot thereof to the other and terminating in a constrictedclosed end tip, said constricted tip decreasing in width from no greaterthan oneeighth inch at a point at least two inches from its apex to nogreater than one-sixteenfth inch at its apex, said means of insulatingmaterial having venting passages therethrough communicating at spacedintervals with at least the constricted tip ci said slot, means formoving said arc into said constricted tip where it is adapted to playuntil extinguished, and means for subjecting said arc to a blast ofuri-ionized gas while playing 1n said constricted tip.

2. In a circuit interrupter cf the air blast type. an arc extinguishingdevice comprising means of non-gas-forming insulating materia-.l havinga tapered notch extending inwardly from one end thereof and a pluralityof spaced venting passages leading from said tapered notch, means forestablishing an arc within the larger portion of said notch, saidtapered notch terminating in a. constricted tip which progressivelydecreases in width to the closed end thereof and which has a width, atits entrance portion to preclude alternating current arcs above apredetermined instantaneous current magnitude from entering therein, andmeans for moving said arc laterally within said notch and into saidconstricted tip following decay of the instantaneous current below saidpredetermined magnitude, said means causing a blast of 1in-ionized gasthrough the are stream and the venting es in said means of insulatingmaterial to assist in extinguishing the src.

3. In a circuit interruptor, means for establishing an arc. anarc-extinguishing structure for extinguishing said arc comprising aplurality of plates of insulating material having through venting spacestherebetween and slots of V-shape in which said arc is adapted to play,said slots decreasing progressively in width from one side thereof tothe other and terminating in the constricted closed end tip, saidconstricted tip de.. creasing in width from no greater than one eighthinch at a point at leastI two inches from its apex to no greater thanone-sixteenth inch at its apex, means for moving said arc into saidconstricted tips where it is adapted to play until extinguished, andmeans for subjecting said arc to a blast of un-ionized gas while playingin said constricted tip.

4. Ina circuit interrupter, an arc-extinguishing device. comprising aplurality of spaced plates of non-gas-formlng insulating material, saidplates having substantially aligned tapered slots extending inwardlyfrom one of their ends means for establishing an arc within the largerportion of said slots, said slots terminating in constricted tips whichprogressively decrease in width to the closed ends thereof and have awidth wt their entrance portion to preclude alternating current arcs-above a predetermined instantaneous current magnitude from enteringtherein, and magnetic means for moving said arc laterally within saidslots and into said constricted tips following decay of theinstantaneous current below said predeterminedl magnitude, said magneticmeans causing a blast of un-ionized gas through the arc stream and thespaces between the plates of insulating material to assist inextinguishing the arc.

5. In a circuit interruptor, an arc-extinguishing device comprising astack of plates of insulating material. means spacing said pistes apreventing passages, said plates being substantially.

determined distance from each other to provide free from maiterialswhich give off gas when acted upon by an arc and having elongatedtapered notches therein, said tapered notches decreasing progressivelyin width from the open to the closed ends thereof and having aconstricted portion of at least two inches in length adjacent the closedends thereof of width to prevent entry thereinto of valternating currentarcs of a predetermined instantaneous current magnitude, means forestablishing an arc within said notches, and means for moving the arcinto the constricted portion of said notches following decay of theinstantaneous value of the arc current below a predetermined magnitudewhere it is cooled and extinguished. i

6. In a circuit interrupter, an arc-extinguishing device comprising astack of plates of insuiating material, means spacing said platea apredetermined distance from each other to provide vent passagestherebetween, said plates being substantially free from materials whichgive oi! gas when acted upon by an arc and having aligned elongatedtapered notches therein, means for establishing an arc within saidaligned notches, and plate means of magnetic material disposed withinsaid stack adjacent the closed ends of said aligned notches to providean intense magnetic field for moving the arc against the closed end oi'said aligned notches where it plays until extinguished, said plate meansof magnetic material being placed in abutting relation with and acrossthe outer edges of a plurality of plates of insulating material so asnot to restrict the venting passages between said plates of insulatingmaterial.

7. In a circuit interrupter,` an arc-extinguishing device comprising astack of plates of insulating material, means spacing said plates apredetermined distance from each other to provide vent passages throughthe stack, said plates being of refractory material and having elongatedtapered notches therein which terminate in a constricted tip decreasingprogressively in width from no greater than one-eighth inch at a pointat least two inches from the closed end of the notches to no greaterthan one-sixteenth inch at the closed end, means for establishing an arcwithin said aligned notches, and plates o! magnetic material disposed atspaced intervals in the stack of plates of insulating material toprovide an intense magnetic field for moving the arc into theconstricted tips of said notches where it plays until extinguished.

8. In a circuit interrupter, an arc-extinguishing device comprisingmeans of insulating material substantially free from material whichgives of! gas when acted upon by an arc, said means of insulatingmaterial denning an elongated V-shaped notch and a plurality of spacedventing passages therethrough communicating at least with the closed endof said notch, means for establishing an arc within said notch, andmeans ofxnagnetic material embedded in said means of insulating materialbut disposed outside said venting passages for producing a magneticfield to move the are toward the closed end of said notch where itisadapted to play without substantial looping into said ventingpassages.

9. In a circuit interrupter, an arc-extinguishing device comprising astack of plates of insulating material, said plates being substantiallyfree from materials which give oi! more than a small quantity of gaswhen acted upon by an arc and having elongated tapered notches extendinginwardly from one end thereof', means spacing said plates from eachother to provide venting passages therebetween in alignment with thelongitudinal axes of said notches, means for establishing an arc withinsaid notches, and plate means of magnetic material disposed at intervalsin the stack but disposedoutside said venting passages for producing amagnetic ileld to move the arc toward the closed end of said notches iand a blast of gas through the arc to aid in extinguishing the arc, saidplates of insulating material being spaced from each other a distance toprevent substantial movement of the arc therebetween.

l0. In a circuit interrupter, an arc-extinguishing device comprising astack of plates oi' insulating material, said plates of insulatingmaterial being substantially free from materials which give of! gas whenacted upon by an arc and having slots of V-shape therein, plates ofmagnetic material disposed between said plates of insulating material oneither side of said slots and extending longitudinally of said plates ofinsulating material to provide vent passages of predeterminedcross-sectional area in alignment with said lots, means for drawing anarc within said slots, said plates of magnetic material providing amagnetic ileld for moving the arc toward the closed ends of said slots,and additional plates of. magnetic material disposed transversely ofsaid longitudinally disposed plates of magnetic material forstrengthening the magnetic reaction for moving said arc, said plates ofinsulating material being spaced from each other a distance to preventsubstantial movement of the arc therebetween.

l1. In a circuit interrupter, an arc-extinguishing device comprising astack of plates of insulating material, said plates of insulatingmaterial being substantially free from materials which give of! gas whenacted upon by an arc and having aligned slots of V-shape therein, platesof magnetic material disposed between said plates of insulating materialon either side of said aligned slots and extending longitudinally ofsaid plates of insulating material to provide vent passages ofpredetermined cross-sectional area in alignment with said slots, meansfor drawing an arc within said aligned slots, said plates of magneticmaterial providing a magnetic ileld for moving the arc against theclosed ends of said aligned slots where it is adapted to play untilextinguished, and additional plates of magnetic material disposedtransversely of said longitudinally disposed plates of magnetic materialfor strengthening the magnetic reaction for moving said arc, saidadditional plates of magnetic material being disposed in abuttingrelation to said plates of insulating material and having sub-4stantially the same thickness so as to prevent obstructing the ventpassages between said plates of magnetic material opposite said notchesto strengthen the magnetic field set up by the arc within said plates ofmagnetic material.

13. In a circuit interrupter oi' the air break type, arc extinguishingmeans comprising a plurality of plates of insulating material, saidplates being substantially free of material which gives off a gas whenacted upon by an arc and having elongated tapered slots extendingtherein from one edge thereof, means for establishing an arc within saidslots, said slots havinor a constricted portion which decreasesprogressively in 'width to the closed end thereof and is so narrow thatalternating current arcs of relatively high instantaneous currentmagnitude will not enter therein but will permit entry only of arcs ofless than a predetermined instantaneous current magnitude, and magneticmeans for moving the arc laterally toward the closed ends of said slots,said arc playing outside said constricted portion until theinstantaneous current has been reduced to said predetermined valuewhereupon it is moved by said magnetic means into said constrictedportion where it is quickly cooled and extinguished- 14. In a circuitinterrupter, arc-extinguishing means of insulating -material comprisinga plurality of plate portions, spaced from one-eighth inch to one-fourthinch apart, said plate portions being free from large quantities ofmaterials which give off a gas when acted upon by an arc and having athickness from one-eighth inch to one-fourth inch, said plate portionshaving slots extending therein from one edge thereof, means forestablishing an arc within said slots, and members of magnetic materialto assist movement of the arc against the closed end of said slots, themagnetic ileld produced by said magnetic members also `causing a blastof cool un-ionized gas to be moved through the arc as it plays againstthe closed end of said slots.

g 15. In a circuit interrupter, arc-extinguishing means comprising aplurality of plates of insulating material, spaced from one-eighth inchto oriefourth inch apart, said plates being substantially free frommaterials which give off a gas when acted upon by an arc and having athickness from vone-eighth inch to -one-fourth inch, said plates havingaligned slots extending therein from one edge thereof, means forestablishing an arc within said slots, and members of magnetic materialdisposed between said plates of insulating material longitudinallythereof on either side of said slots to assist movement of the arcagainst the closed end of said slots, said members of magnetic materialserving to space said plates of insulating material apart and be` ingdisplaced laterally from each other so as t provide a venting spacebetweenadiacent plates of insulating material having a cross-sectionalarea 'of from one-eighth square inch to threefourths square inch, thethickness of said plates of insulating material. the spacing betweensaidplates and the cross-sectional area of said venting spaces cooperatingto prevent substantial lengthening of the arc and movement thereofbetween said plates of insulating material.

ld. In .a circuit interrupter, arc-extinguishing means comprising aplurality of spaced plates of insulating material, said plates ofinsulating material being of substantially refractory material andhaving elongated tapered notches therein aligned at least at the openends thereof, a pair of contacts at least one of which is adapted to bemoved within said aligned notches to establish an arc therein, and meansdisposed on either side of the path of movement of said movable contactadjacent the open ends of said aligned notches and arranged toclose theopen ends of said notches except for the space required for contactmovement to cause the gas produced by said arc upon separation of saidcontacts to expand laterally and in a direction away from said contactsso as to prevent said gas from being blown out of the open end of saidnotches.

1'7. In a circuitI interrupter, arc extinguishing means comprising meansof insulating material having an elongated V-shaped groove extendinginwardly from one end thereof, said means of insulating material havingspaced venting passages therethrough communicating With said groove,contact means separable within the open end of said groove forestablishing an arc, and lining members disposed laterally of saidcontact means and arranged to close in part the open end of said grooveto prevent arc gases from being blown out of said groove in thedirection of said contact means.

18. In -a circuit interrupter, arc extinguishing means comprising aplurality of plates of insulating material each of said plates having anelongated V-shaped slot extending inwardly from one end thereof, meansspacing said plates from each other to provide venting passagestherebetween, con'tact'means separable within the open ends of saidslots for establishing an arc, and deiiecting members of insulatingmaterial disposed laterally of said contact means adjacent the ends ofsaid plates to substantially close the spaces between said plates oneach side of said slots, said deecting members extending inwardly withrespect to the open ends of said slots to provide a constricted entrancepassage to saidslots for preventing arc gases from being blown out ofsaid slots in the direction of said contact means.

19. In a circuit interrupter, arc extinguishing means comprising aplurality of plates of insulating material having elongated V-shapedslots extending inwardly from .one end thereof, means for establishingan arc withiny said slots, andplates of U-shaped magnetic materialdisposed between said plates of insulating material having the legs ofthe U on opposite sides of said slots for moving said arc towards theclosed ends of said slots, the transverse portion of said plates ofmagnetic material extending beyond the plates LEON n. LUDWIG.

